Problem: $-\dfrac{5}{4} - \dfrac{9}{6} = {?}$
Answer: $ = - {\dfrac{5 \times 3}{4 \times 3}} - {\dfrac{9 \times 2}{6 \times 2}} $ $ = - {\dfrac{15}{12}} - {\dfrac{18}{12}} $ $ = - \dfrac{{15} - {18}}{12} $ $ = -\dfrac{33}{12}$